Robin Carey robin_carey5 at yahoo.co.uk
Wed Apr 11 03:11:39 PDT 2007

What is the point of keeping/using the in-kernel arc4
random number generator when you already have a very
good/superior IBAA/L15 random number generator.

If you need a u_int32_t quantity then simply add a
function to /sys/kern/kern_nrandom.c to produce a


Some issues with /sys/libkern/karc4random.c :

(a) If you intend to keep /sys/libkern/karc4random.c I
recommend you make a modification to it to improve
performance: Every time the karc4_random() function is
called it calls getmicrotime(), to check the time, and
it also checks the number of runs made, to see if it
should reseed itself. You can make a big performance
improvement by removing this call to getmicrotime()
and instead simply checking the number of runs to
determine when it should reseed itself.

(b) The karc4random.c file uses u_int8_t types for
arc4_i, arc4_j and arc4_t so there is no need for the
% 256 operation - another performance improvement.

(c) In arc4_init() you are throwing away 256*4 bytes
of output, when you only need to throw away the first
256 bytes of output.

R Carey.

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